I think I have SPF up and running now. So I am onto the DomainKeys implementation.
Here is a snippet of the results of netstat -tap (I removed all apache, mysql, and tcp6 lines as I didn't think they were important):
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 localhost.localdo:60000 *:* LISTEN 6564/postgrey.pid -
tcp 0 0 localhost.localdo:10024 *:* LISTEN 6430/amavisd (maste
tcp 0 0 localhost.localdo:10025 *:* LISTEN 13100/master
tcp 0 0 localhost.localdo:spamd *:* LISTEN 6568/spamd.pid
tcp 0 0 *:smtp *:* LISTEN 13100/master
tcp 0 0 localhost.localdom:8892 *:* LISTEN 13173/dk-filter
When I enable the following lines in the Postfix main.cf file by uncommenting them, I cannot send email.
milter_default_action = accept
milter_protocol = 2
smtpd_milters = inet:localhost:8892
non_smtpd_milters = inet:localhost:8892
Instead, I get an error from Outlook saying:
Reported error (0x800CCC6A) : 'Your outgoing (SMTP) e-mail server has reported an internal error. If you continue to receive this message, contact your server administrator or Internet service provider (ISP). The server responded: 451 4.7.1 Service unavailable - try again later'
In my mail log, I see the following:
Sep 27 22:26:24 gopher dk-filter: D2702C0CC18: dk_getsig(): resource unavailable: PEM_read_bio_PrivateKey() failed
Sep 27 22:26:24 gopher dk-filter: D2702C0CC18 SSL error:0906D06C:PEM routines:PEM_read_bio:no start line
Sep 27 22:26:24 gopher postfix/cleanup: D2702C0CC18: milter-reject: END-OF-MESSAGE from unknown[192.168.100.2]: 4.7.1 Service unavailable - try again later; from=<email@example.com> to=<firstname.lastname@example.org> proto=ESMTP helo=<xxxx>